In engines wherein a combustion force is converted to a rotational force via a crankshaft, torque fluctuations are inevitably produced in the crankshaft. These torque fluctuations cause rotational fluctuations of rotating members which give rise to vibration or noise. In a four cycle, four cylinder engine, for example, such changes are brought about by a second order torque variation, and in a six cylinder engine by a third order torque variation.
Jikkai Sho 59-24550 published by the Japanese Patent Office discloses a flywheel in which a rolling chamber is formed, this chamber containing a damping mass which is free to roll. The damping mass executes a pendulum motion in a radial direction of the flywheel while rolling on the wall of the rolling chamber as the engine rotates, and thereby displaces the center of gravity.
In such a case, if the distance from the flywheel rotation center to the pivot center of the pendulum motion of the damping mass is R, and the distance from this pivot center to the center of gravity of the damping mass is L, rotational fluctuations of rotating members can be reduced by setting the ratio R/L equal to the square of an engine torque fluctuation of order n.
On pages I-57-I-58 of Kikai Gakkai Koen Ronbunshu (Collected Papers of the Institute of Mechanical Engineers of Japan), (1937), Vol. 6, No. 24, it is disclosed how the dimensions of each member are determined with regard to moment of inertia, and on pages I-47-I-53 of the same reference, a theory is disclosed which takes account of attenuation due to friction when a weight is disposed at an off center position with respect to the center of rotation of the rotating axis.
If the damping mass of a flywheel were also designed taking account of moment of inertia in this way, it would be theoretically possible to provide better reduction of rotational fluctuations.
It is however impossible to completely eliminate manufacturing errors, and there was therefore always a risk of a minor discrepancy arising between the dimensions of a flywheel and optimum values found from theory. In addition, dimensional variations of parts were caused by wear. Moreover, it was difficult to theoretically calculate the attenuation due to friction between the rolling surface of the damping mass and the wall of the rolling chamber, and this value changed with the extent of wear.
Therefore, It was extremely difficult to manufacture a flywheel having dimensions exactly the same as the optimum theoretical values, and to maintain these dimensions over a long period of time.